1. Field of the Invention
This invention is directed to the art of corrugated plasticboard manufacture. Two faced corrugated plasticboard is an article of manufacture having a sandwich structure wherein two face sheets are heat bonded to and separated by a corrugated core. The materials comprising the core and face sheets can be any material providing a compatible heat fusible or heat sealable surface. 2. Prior Art
Plasticboard having a corrugated core generally is made either by single-piece extrusion using an integral profile die demonstrated by the Covena Company of Italy or by extrusion lamination of two molten plastic films to a corrugated core as disclosed in U.S. Pat. Nos. 3,837,973 (1974); 3,682,736 (1974); and 3,833,440 (1974). In the case of the single-piece extrusion method, the process is limited in that (1) the flutes of the corrugated core run parallel to the extrusion or machine direction, (2) the entire board is of the same material and (3) the process's maximum practical speed is about 17 feet/minute. In the case of the extrusion lamination, the process is limited in that careful annealing is required to avoid warping and/or formation of a wavy surface and in that the process's maximum practical speed is about 40 feet/minute.